Dynamo-electric machine



May 5, 1925.

1,536,077 F. cREEDY DYNAMO ELECTRIC MACHINE Filed m1151430, 1921 '7 sheets-sheet l May 5, 1925. 1,536,077

F. CREEDY DYNAMO ELECTRI C MACHINE rjilegquly, 30, 1921 7 sheets-sheet 2 May 5, 1925. 1,536,077

F. CREEDY DYNAMO ELECTRI C MACHINE Filed JulyV 3 0, 1921 7 Sheet-Sh'eef.` 5

May 5, 1925.

Y F. CREEDY DYNAMo ELECTRIC MACHINE May 5,1 1925.

1,536,077 F cREEDY DYNAMO ELECTRIC MACHINE Filed July 30, 1921 'I Sne'etssht 6 o o @e /fwE/vra .f5/ iw? May 5, 1925. 1,536,077

F. CREE-DY DYNAMO ELECTRIC MACHINE Filed July 30, ,1921- 7 SheetsShet 7 Patented May 5, 1925.

UNITED STATES FREDERICK CREEDY, OF ILKLEY, ENGLAND.

DYNAMG-ELECTRIC MACHINE.

Application filed July 30, 1921. Serial No. 488,687.

Ireland, and aA resident of 10 Ashburn Place, Ilkley, Yorkshire, England, have invented certain new and useful Improvements in Dynamo-Electric Machines (on which application has been made for Letters Patent in Great Britain, No. 23,123, tiled 5th August, 1920; No. 36,540, tiled 30th December, 1920), of which thel following is a specilication.

This invention relates to windings for dynamo electric machines which require to operate on tields ot more than one r,pole number. Examples ot such machines are the variable pole machines described in my tormer Patent No. 12914124 and my application Serial No. 276263 tiled Feb. 11th, 1919; other examples are the now well known internal cascade machines which combine Aupon one carcase the windings or the equivalent -ot the windings ot two cascade connected machines; various developments otsuch machines are described in my co-pending application of even date with this.

The purpose of the invent-ion is to provide windings ot simple form capable of use upon a plurality ot pole numbers. More specific purposes of the invention are to provi-de windings capable of use as primary windi-ngson one or more pole numbers andA simultaneously as secondary windings on another or others; or capable fol" use as secl-` as a primary winding upon a plurality et pole numberg7 the Change m 4P019 number.

requiring no changes in the connections o-t the sections of the winding among them-v selves other than such as result `trom changes of the connections between the ter-A minals and supply phases. My invention, further, and more specifically includes a star-mesh network, in' which alternate sections term the mesh (or meshes), and alternate sections in the mesh are mutually reversed, while also alternate sections in the star are mutually reversed. Moreover in its fullest embodiment my invention includes a. dynamo electric machine having a winding ot this kind upon one or both oit' its numbers and equipped with the simple control apparatus necessary to bring about desired changes oit pole member or resistance control. The term section employed in the present specification is to be understood to mean onevor several coils of the winding joined in series, this coilor coils lying in a pair or several pairs ot slots.

In the accompanying dra-wings,

Figures 1 to 4- represent and explain a winding typical ot my invention, together vith certain modifications thereot.

Figure 5 shows another suchwinding together with the supply and control apparatus requisite for variable pole working.

Figures 6 to 10 explain the use ot this winding and the eti'ect ot' its control apparatus. n

Figure 11 shows yet another such winding with supply -andcontrol apparatus.

Figure 12 further illustra-tes the eiiect of its control apparatus.

Figures 13 to 15 similarly illustrate another `class of windino" typical of my invention. Figure 16 shows the stator and rotor windings ci: -a six speed motor.

In my Patent No. 19.91%24 I have shown how a simple star-connected or mesh-counected windingmay be caused to produce any one ot' a number of pole numbers by the application ot E. M. F.s of appropriate phase to its terminals. In my application Serial No. 276263 I have shown how a star-mesh connection ot the sections ot a winding may be used to produce in the windin Y a greater number of phasesfthan. that or' the external supply. I have now found that it vthe star-mesh winding be built up by combining the sections in certain definite ways further explained hereinafter, the winding will serve as a primary winding on any pole number whatever, except a pole number which is equal to halt the number ot sections, provided the number ot' sections is sui'iicient to keep the phase diti'erence between neighbouring sections within the limit discussed in my spcciication Serial No. 359311 tiled February 17th, 1920.

Figure 1 shows winding ot 12 sections built in tue manner in question, and adapted to produce 2, 4, or 8 poles withoutrchange in the connections of its sections illustrated. The sections are supposed numbered consecutively around the circumference, and the number of each section is indicated inV the circle which represents,.say, the beginning of the section proceeding clockwise around the machine. It will be seen that alternate sections are connected into a mesh,

and the remaining sections are connected as star rays to the angles of the mesh; further, alternate sections of the mesh are reversed, and so are alternate sections of the star; and vfinally where the beginnings of two mesh sections are joined together, the end of the intervening star section is joined to them, while where the ends of two mesh sections join, the beginning of the intervening star section is joined in them.

In the figure the sections are marked with the phase angles they must have if the Vwinding is to produce 2 poles; and they are also marked, with the figures underlined, with the phase angles appropriate to 4 poles. Since it makes no difference to the operation of the winding if the phase of all its sections is changed by the same amount, it is clear that the 2 pole arrangement does not require any different phases of supply from the 4 pole arrangement, for

if 300 be added to its phase angles those of the star sections become the same as, or opposite to, one or other of the supply phases for 4 poles. This is more readily seen from Figure 2 which shows the phases of the sections for 2 poles, section 1 being changed in phase 30 as compared with its 4 pole condition. Figure 2 (and Figure 1 for the 4 pole condition) represents by `the direction in which its sections are drawn the phase of the E. M. F. in the sections; and use is made of this graphic representation of the phase angles in most of the figures described below.

On 6 poles alternate star sections are in lopposition of phase; in other words when producing this pole number the Vwinning admits only of single phase excitation and gives the machine the properties of a single phase induction motor rather than of a'polyphase induction motor. This'is true of any winding connected in this manner for a' pole number equal to half its number of sections; so that for many purposes it is not convenient to employ the winding on this pole number. V

Figure 3 representsY a 12 section winding on 8y poles. As compared with Figure 1 the star sections are reversed. But it is not necessary to change the connections of the winding to secure this effect. Figure 4 shows the same phases in the sections, and is arrived at from Figure 1 merely by shortcircuiting the star terminals leaving the mesh angles to be con este-d to the supply.

This illustrates another general property' of these windings; they may be changed from a given pole number less than half the number of sections, to another pole number as much greater than half the number of sections as the first was less, by reversal of half the sections. The subst-itution of the Figure 4 arrangement for that of Figure 3 can only be thus simply effected for a 12 section winding, since it depends on the fact that the radius to the angle of the heXagon is equal to its side, which is not the case with other polygons.

For reasons of economy in the number of supply phases needed, and also where a winding is to serve as a secondary on one pole number in addition toV acting as a primary on another, it is often an advantage if several terminals of the winding are con-V nectedto the same phase of supply; as the terminals of the 2 pole winding of Figure 1 are connected in pairs in Figure 2. The number of terminals connected together is the common factor of n and where n is the number of star sections and p the number of pole pairs. From the characteristics of the winding already set forth it is apparent that the number of sections must be divisible by 4, i. e., n must be even. lf g is odd, then Whenever p is also odd Y L ce is even then the terminals ship between the current and the E. M. F.

in each section is the same.

AS an example of the use of this type of winding for variable pole working, Figure 5 shows a winding lV of 36 sections, together with the transformer Tr and a controller C0 necessary to enable it when supplied from three-phase mains to produce 6, 8, 10, 12, 14 or 16 poles. The supply mains are connected to the alternate angles L1, L2, L3, of the transformer. The controller consists of four 9-pole two-way switches, and one 2-pole two-way switch. The contacts and knife blades of the switches are connected to the tappings of the transformer or the sections of the windtransformer, and in conjun-'ctionwith the other tour switches brings about lthechanges in the. phase oi? the sections shown' in Figures to 10, in which figures theA direction in which each section is drawn representsits phase as above explained. The two po-Y sitions of the respective switches are in'dicated by the letters A-J respectively. ItA

A, C and I alone are closed the winding has the phases shown infFigure 6, it has 6 parallels and produces 6 poles.- It B, D

and J are closed the winding isconiiected' as in Figure 7 and `gives 8 poles. I'A, B and I are closed, the winding is connected as 'in Figure 8, lias-two parallelsfand produces 10 poles. It C, E, andJ are closed the winding has the phases shown in Figure 9, has three parallels and produces 12 poles. It A, F and I are closed the winding has the phases indicated iii Figure 14,

has two parallels and .produces lltA poles;l

Finally it Vswitches G, H, and I are closed the phases ot the wind-ing are those shown in Figure and the winding producesv 16 poles. Examination ot the iigures will show that in all ot them the winding yretains the connections'between` its sections shown -in Figure 5;itis only the connections to lthe'supply that are changed', rthough obviously the connection ot `two or more sections to the saine phases-Of th'e sufpply may also be regarded as a new connection in the winding.

It will be. noted that tor 8 poles 11S supply phases are required,- and la less num# ber may be en'i-ployed tor certain other 'pole numbers. For this reason a transformer 'll/r is used capable ot transforming a tlirce phase into an 1S-phase supply. rThe lesign ot transformers tor such phase multiplication has been described in my specification Serial No. 276263.

That specii'ication points out, also,A that the voltage applied to each section of the winding on its 'ditte-rent pole "numbers 'ought to decrease as the corresponding speed ot the machine decreases, "and that 'consef the arrangement of Figure for on G 1poles tlieie are three sections between, say, line terminals L1 vand L?, while on 12 poles there are tout', and on 14 :poles appronimaitely live.

Naturally the 'controller and transformer ot Figure lmay be simplified it' not all the pole numbers described are required. For instance, it only and 1-2 poles are required, the sections shown joined in parallel on 12 poles may be permanently connected together, and the controller need only effect connections between diametrically opposite points ot the 12 pole diagram to bring about the production of 6 poles. Similarly it 6 10 and 14 poles alone are required, the terminals which are connected 'on the 10 and 11 pole diagrams may be connected permancntly, and it the controller is arranged to join these terminals together in .sets ot three spacedei'enly around the circuuitcrence it will produce the 6 pole connection, Comparison ot' the diagrams tor 8 and 10 poles shows that terminals 1, 9, 17, 25, 5, 123, 21, 29, occur inthe saine order on botli pole numbers reading clockwise on 8 pole and counter-clockwise onv 10 pole. Hence, switch B by which these tciminals are 4connected to evenly `spaced supply phases may remain closed for both otthese pole numbers, the necessary `change of phases being eitected 'by throwing over vthe two pole switch from ,I to I so reversing the direction ot rotation ot the flux. This is because on niii-irb'ers ot poles-spaced equally above andbelow 1/4 ot tlien-iiinlber ot sections lthe same phases of' supply are required at alternate terminals but taken clockwise for the one pole number and anti-clockwise tor the other.

All these pole numbers except 12 poles may be produced -by a winding ot .24 sections. Otlier numbers of Sections are also possible; but if the yultimate 'supply is threephaseit is of advantage to use numbers of sectiondii'isi-ble by three, Figure 11 shows a winding w of 24; sections with its supply transformer Tr and controller C0. It 'will be seen that the winding consists 'ot two completely independent star vmesh networks. each like that of Figure El, and'each capable ot' connection in parallels like Figure llic transformer is vrcoiiired to gire six evenly spaced phases, and in addition, phases displaced fTl/O and'22l/O on each side ot three of these vsix phases. The controller coinprises ftwo 6-pole one-way switches P and Q, andi two' Gpole two-way switches Ils S and T, U, togetl-ierwith a two-pole two-way reversing switch V, lV.

The contacts and plates ot the switches are connected to the .tappi-'rigs ot' the transformer and the sections ot the windings whose lreference numbers and letters 'thev bear. Most ot the connections are `omitted for simplicity, but as an example (il, l2. tt

show typicalX connections from the trans-- former Tr to the 'controller C0 and Z-, Z2, Z3, Zt, ZZ show typical connectionstroni the controller switch (lo to section terminals ot the motor winding.

On 8 poles P, R and V are closed, and on 1G poles P, S, and lV. For both of these pole numbers the condition of the winding is represented by Figure 11; the connections of one half of the winding, the part X of Figure 11, are unchanged, except for the reversal of order ot the phases due to thev alters the phase difference between corresponding sections of the two pai'ts from 15o to 195o. The condition or' the winding on both pole numbers is as shown in Figure 12, but the phases of the one part are shifted with respect to those of the other. Tt will be understood that the directions of the lines representing the sections of `the windings constitutes an indication of the phase of the E. M. F.s, and also of the currents, in such sections. Thus, for example, in Fig. 11 the phase of the E. M. F. in the section numbered 17 may be considered to be zero, whereas, when the winding is connected in the manner illustrated in Fig. 12 the E. M. F.V

in the section 17 is of phase 112%". This is indicated by the direction of the line representing the section 17 in Fig. 12.

Another star-mesh connection serving the same purpose is shown for 24 sections in Figures 13-15, the sections are connected in two groups, the odd sections forming one group and the even sections the other, as shown in Figure 13. Vithin each group pairs of opposite sections are connected in series, but in alternate pairs the sections of the pair are mutually reversed. It will be clear that the arrangement of Figure 13 can be extended to any number o'f sections divisible by eight; so that the i-section winding shown is typical ot' a class of windings.

Figure 'lll shows the connections of this winding for producing 8 poles (save that two switches s, s are shown open for prominence). The .two groups ot' sections are joined in series, and the pairs ot' sections in opposition in the drawing of Fig. 13 form star arms connected to the junctions of a mesh composed of the remaining pairs. For 10 poles each group is closed upon itself as shown in Figure 15, and the pairs in which the sections are not mutually reversed in the drawing of Fig. 13 form the star arms. To effect this change the switches s, s are oper-I ated to connect the sections 24 and 14 and the sections 3 and 5.

As has been shown in my former specifications,it is easy to determine the phases which the sections of a winding require to have upon any particular pole number. There can then be no difficulty in constructing controller which will connect the sections to the requisite phases. But in general such a controller might be very complica-ted if advantage were not taken, as in the two in stances described, of such symmetry in the phase changes as may occur on the particular set of pole numbers required. Such possible simplification may be readily deduced in the light of the following general rule governing the phase changes.

If the winding comprises r equally spaced groups of P+C@ sections each, the relative phases of the sections in each group will be the same on P pole pairs and Q, pole pairs. The relation between their actual phases may be expressed by saying that for Q pole pairs as compared with P pole pairs each group is reversed round one of a set or' 'l' equally yspaced axes, of which the iii-st, round which group 1 is reversed, passes through section l of that group, and .those round which the remaining groups'are reversed are to betaken inthe same order as the groups i. e. group 2 reverses about an 7T axis diering in position in space from the first axis, group 3 about one differing 2;

Winding In, round one differing The statement that a group of sections is reversed about a particularV axis in space in changing from P pole pairs to Q pole pairs, the relative phases of its sections re# maining unaltered, is meant that any section distant by a given amount in a clockwise direction on P pole pairs has the same phase as a section distant by the same amount in a counter-clockwise direction on Q, pole pairs. Y

It has been shown that the star mesh winding can be used as a primary winding on any one of several pole numbers. The winding acts as a cascade winding if alternate star terminals are shortfcircuited and the remainder left on open circuit, as isn more fully explained in my application of even date herewith; and the connection o'l these open-circuit terminals, for instance through resistances, is a useful means of bringing a cascade motor up to a basal speed. The motor may be brought up to its cascade speed with half the terminals opencircuited, byV connecting resistances across tappings in the primary winding oi' the inachine; but, instead, the terminals of the secondary Which require to be short-circiiited on the cascade speed may for starting be connected through variable resistances. It the motor is also required to rise to a basal speed, a single set of slip rings and resiste ences may be gepland; teetherwith switchy upon the rotor which for running up to cascade speed connects to the slip rings llt) . connects to the slip ringsl the alternate star terminals for running on cascade speed and inY readiness for running up to a basal speed.

But, in addition, wheneverv the terminals of a star mesh winding are connected together in pairs or in larger sets as in Figure G or 9, the winding will act simultaneously as a primary on one pole number and as a secondary on another. For instance, the -pole connection of Figure 6 admits of 10- pole secondary currents circulating in the circuitsv which are closed by the junction of the terminals in sets of six, that is by joining the ends of the sections 1, 7, 13, 19, 25, 31, the ends of the sections 33, 27, 21, 15, 9, 3. and the ends of the sections 5, 11, 17 L3, 29, 85; so that this winding could serve, tor instance, as the primary of an internal cascade motor. producing' six poles and acting as a secondary on 10 poles.

Further, if the star mesh winding is used only as a. secondary it willfserve as a shortcircuited secondary on one pole number and enable resistance control on another. For instance, if the terminals ot Figure 6 are permanently connected in sets of six, and resistances are joined between the three terminals thus formed, the winding gives resistance control when acting as a secondary on 6, poles, and on other pole numbers acts as a short-circuited secondary. So a motor might be built with a primary winding capable of giving say G and 8 poles, which primary might itself be such a ywinding as is shown in Figures 6 and 7, and with a secondary as just described; and it Could be brought up to its S pole speed by connecting` the primary for 6 poles and running up on resistances, and when the S-pole speed was reached changing the primary to its 8 pole connection would cause the" machine to continue running at S-pole speed with short-circuited secondary. It is obvious the principle can be extended to a motor with Several speeds, :tor instance, to one with a primary winding and controller capable oi all the connections of Figures to lO; and it offers a convenient means of passing' from one speed to another without shock.

,Finally a. comparison of Figures 1 and 3 `shows that the provision of a switch itor rcversing the star sections with respect to the mesh sectionsadds considerably lto the number oi pole numbers upon which one ot these. windings will serve, For instance, the winding otl Figure 5 has enough sections to admit of the production of 211 poles without the phase difference between neighbouring sections exceeding' 1200. Therefore, the addition to the control apparatus of that tigure ot'y switches for reversing the star secthe production oi all pole numbers from to 24j except 18. Save tor the reversal of the star sections the connections tor 20 poles would be the same as vtor 16, ttor 22 poles the` same as for 14, and so on.

lit will be obvious that the complete embodime-ntI ot' my invention is a dynamo electric machine bearing one or more of such windings as have been described upon one orv both of its members. As a specific instance., Figure 16 shows the windings of one toi-1n of motor according to the present invention. 1

The motor has a winding on the stator SW of 36 sections. T1 is the transformer. and C0 the controller to enable the winding when supplied from three phase mains, to produce G, S, 10, 12, 14 or 1G poles. Most oli' the connections are omitted but X1, X2, X1 show typical connections from the trans- Jformer TrV to. the controller C0, and Y1, Y2, V3 show typical connections from the controller Co to the section terminals ot the motor winding. The winding SW is ofV the form illustrated in Fig. 5 or' the drawings and has been fully described with reference to said ligure. The rotor winding comprises two completely independent star mesh networks RVV1 and RV2. The winding has 24 sections, and is of the form illustrated in Fig. 1101 the drawings which has been fully described above. To enable this windingA to be u sed as a secondary, control apparatus must be provided for connecting together directly or through resistances the terminals ot the winding. C01 is a switch provided tor this purpose in combination with the controller C0. The resistances are lettered V1, V2, V3, V1, V5, V, V1, V8, V9, V10, V11, V12, and the switch is so arranged that` the winding may be connected to the transformer Tr when it is to be employed as a primary or its terminals may be short circuit-ed through the resistances V1, V2, V3, V4, V5,` VG, V1. V8, V2, V10, V11, V12, or directly connected together when it is employed as a secondary. The connections of the star sections to the switch C01 are shown in the conventional way Z1, Z2, Z1., Z4, Z5 and Showing typical connections.

The motor is arranged kto run on 6, 8, 10, 12, 14 and 16 poles, the stator winding- SV producing these. The star mesh winding` on the rotor acts as a secondary on these pole numbers.

By operating the controller (lo for the stator winding as indicated in the ligure, the connections are obtained to produce thc necessary arrangement of the stator windings tor the motor to run on any of the speeds mentioned; the amount of resistance connected into the rotor winding RVV1, RV2 will be varied as required. For example, to produce 8 poles the Switches B, D and J tiens with respectto the mesh would enable are closed, and to produce 1G poles the switches G, II and I are closed as is described with reference to Figure of the Y accompanying drawings.

The winding RW, Rim may be used as a primary by operating the switch C01 to connect the winding through the controller C0` to the supply, as has been described above.

What I claim is 1. In analternating current dynamo electric machine comprising a stator member and rotor member, a winding on one of said poles without changes in the connections of' the sections of the winding among them-V selves.

2. In an alternating current dynamo electric machineV comprising a Vstator member I, and rotor member a winding on one of said members to be energized from` a polyphase V supply and so disposed as to generate E.

M. Ffs of anumber of phases greater than the number of phases in the supply, said Vwinding having halt its sections connected in mesh, the remaining sections connected in star to the Vjunctions of mesh sections, alternate sections of the mesh mutually reversed and alternate sections of the star mutually reversed and means to connect said winding in a plurality of ways to operate with a plui rality of fields of different numbers of poles without changes in the connections of sections among themselves.

3. In an alternating current dynamo electhe tric machine comprising a stator member and rotorV member, a Winding on one of said members toV be energizedfrom a polyphase supply and so disposed as to generate E.V M.

Ffsof a number of phases greater than thev Vnumber of phases in the supply, said Winding having half its sections connected in mesh, the Vremaining sections connected in star to the junctionsof mesh sections, alternate sections. of the mesh mutually reversed and alternate sections of the star mutually reversed and means to connect s'aidvvinding in la plurality of ways to operatewith a plurality of iields of different numbers of poles without changes in the connections of the sections among themselves, the number of star connected sections having a common factor with the difference between'half of "said number and each of thenumber of pole pairs produced by the winding, saidY .Y common factor being not less than two.

4. In an alternating current dynamo electric Vmachine comprising a stator member and rotor member, aavinding on one ot said members to be energized from a polyphase supply and so disposed as to generate E.

M. F.s of a number of phases greater than rality oit ways to operate with a plurality ol? Yiields of different numbers of poles without changes in the connections of the sections among themselves, and' so that the number of sections in series between the terminals ot the winding having approximately a given phase diiference is less as the number of poles in the ield produced by it is less. Y

5. In an alternating current dynamo electric machine comprising a stator member and rotor member, a winding on one of said members to beenei'gized from avpolyphase supply, comprising a plurality of independent sets of sections, each set of sections being permanently interconnected so that the number of pha'ses'produced in it will be greater than the number of terminals of the set, while the pole number of the winding is changed by changing the phases of the sets without changing the connections of the sections within the set.

6. In an' alternating current dynamo electric machine comprising a stator and rotor, a primary winding having alternate Vsections ccnnected in mesh and theremaining sections connected in star to the angles of the mesh, with means for joiningthe star terminals together in sets and to supply vphases whereby the winding will produce a of phases greater than the number of phases inthe supply and means to connect said windings in a plurality of ways to operate with a plurality of fields of different numbers of poles without changes in the connections ct the sections of the windings among themselves. Y

8. In an alternating current dynamo electric machine, comprising a stator member and rotor member, a plurality of windings onv one of said members to be energized from a polyphase supply and each so disposed as'to generateE. M. F.s of a number of phases greater than the number of phases in the supply, sequential sections of windingaroundrthe periphery ot the member constituting parts of diierent windings, al-

miY

ico

ternate sections of each winding being connected in mesh the remaining sections connected in star to the junctions of the mesh sections and means to connect said windings in a plurality of Vays to operate with a plurality ot' tields ot different numbers ot' poles without changes in the connections of the sections among themselves.

9. An alternating current dynamo electric machine con'iprising a stator member and rotor member, a winding on one of said members to be connected to a polyphase supply and so disposed as to generate E. M. F.s of a number of phases greater than the number of phases in the supply, said winding having halt its sections connected in mesh, the remaining sections connected in star to the junctions of mesh sec tions, alternate sections ot the mesh mutually reversed and alternate sections of the star mutually reversed, means to conneet said winding to the supply in a plurality oit ways to produce a plurality of lields of different numbers of poles without changes in the connections ot' the sections among themselves, and a winding on the other member adapted to act as a secondary in the fields produced by the winding on the lil-st mentioned member.

l0. An alternating current dynamo electric machine con'iprising a stator member and rotor member, a winding on one of said members to be connected to a polyphase supply and so disposed as to generate E. M. F.s of a number of phases greater than the number of phases in the supply, said winding' having alternate sect-ions connected into a mesh ot' an even number of sides exceeding six, the remaining sections connected in star to the junctions of the mesh sections, said star sections including a diiilerent number of turns than said mesh sections, means to connect said winding in a plurality of ways to produce a plurality o'l" tields of different numbers of poles without changes in the connections of the sections among' themselves, and a winding on the other member adapted to act as a secondary in the ields produced by the winding on the first mentioned member.

11. An alternating current dynamo electric machine comprising a stator member and rotor member, a winding on one of said members to be connected to a polyphase supply and so disposed as to gene-rate E M. F.s oit a number of phases greater than the number of phases in the supply, said winding having halt its sections connected in mesh, the remaining sections connected in star to the junctions of mesh sections, alternate sections of the mesh mutually reversed and alternate sections of the star mutually reversed, means to connect said winding to the supply in a plurality of ways to produce a plurality of lields of different numbers of poles without changes in the connections ot the sections among themselves, and a plurality of windings on the other member, each comprising a star mesh network, sequential sections of winding around the periphery of the member constituting parts ot' diiferent networks, alternate sections of each network being' connected in mesh and the remaining sections in star with the junctions ot' the mesh and means for connecting said star sections to enable the windings to act as secondaries in the lields produced by the windings on the irst mentioned member.

l2. In a variable pole alternating current dynamo electric machine comprising a stator member and rotor member, a winding on one of said members in which alternate sections are connected in mesh and the remaining sections in star to the angles ot' the mesh, said winding being arranged to act as a secondary upon a plurality ot pole numbers and means whereby resistance may be inserted in the circuit thereot` for control on one pole number.

In witness whereof I have signed my name to this specilicat-ion.

FREDERICK CREEDY. 

